Overview

The discovery of cell-free circulating tumor DNA (crDNA) in blood and the maturation of technologies for ctDNA analysis have presented an attractive opportunity for minimally invasive "liquid biopsy" genomic diagnostics. The investigators plan to perform EUS-guided portal vein and hepatic vein aspiration in GI cancers patients. The aim of the current study is thus to examine the concentration of ctDNA in portal vein (EUS-guided PVA), hepatic vein (EUS-guided HVA) and peripheral blood to understand the first pass effect of the liver with gastrointestinal (GI) cancers, and the possibility of using ctDNA as a marker for preoperative staging, restaging after neoadjuvant chemotherapy, and monitoring for recurrence.

Eligibility

Inclusion criteria:

1. Age >= 18 years old
2. Newly diagnosed stage II-IV distal gastric cancer, pancreatic cancer or colorectal cancer
3. Undergoing treatment with either:
   1. Surgery
   2. Neoadjuvant chemotherapy
   3. Neoadjuvant chemoirradiation
   4. Palliative chemotherapy/ immunotherapy

      Exclusion criteria:

   5. Synchronous cancer of other sites
   6. Cardia, high lesser curve tumors, oesophagogastric junction tumors
   7. Presence of bulky lymph nodes at lesser curve/ coeliac region precluding a clear EUS puncture site to portal vein and hepatic vein
   8. Patients with coagulopathy (international normalized ratio >1.3, partial thromboplastin time greater than twice that of control), platelet count <50,000x103/uL
   9. Patients unwilling to undergo follow-up assessments
   10. Patients with liver cirrhosis, portal hypertension and/ or gastric varices
   11. Patient refusal to participate

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